The present invention relates to a fluid pressure control valve apparatus for a clutch or a brake.
As a conventional clutch hydraulic control apparatus, for example, the one disclosed in Japanese Patent Laid-open No. 63-235732 is known. FIG. 12 and FIG. 13 are a hydraulic circuit diagram of a clutch oil pressure control apparatus and a sectional view showing a constitution of an oil pressure control valve in the control apparatus, which are disclosed in Japanese Patent Laid-open No. 63-235732.
In FIG. 12 and FIG. 13, a control valve 2 for controlling a clutch cylinder 1 has a pressure control valve 80 for controlling a clutch pressure, a flow detecting valve 70 for detecting a flow inside the clutch cylinder 1, and a sensor section 3 for detecting a filling in the clutch cylinder 1 and a clutch pressure. The pressure control valve 80, the flow detecting valve 70 and the sensor section 3 are housed in an integral housing 78. The control apparatus has a controller 90, the pressure control valve 80 is controlled by the controller 90, and a detection signal S of the sensor section 3 is inputted into the controller 90. The clutch cylinder 1 is connected to a clutch not shown.
The pressure control valve 80 has a spool 81 directly operated by a plunger 83 of a proportional solenoid 82 driven with a thrust force corresponding to a magnitude of a command current I from the controller 90 to control an opened amount thereof, and controls the clutch pressure. The flow detecting valve 70 feeds oil to the clutch cylinder 1 via an orifice 75 provided at the spool 71, and when a fluid is filled in the clutch cylinder 1, then the fluid flow is stopped and pressure is built up, the flow detecting valve 70 is moved by a difference in pressure receiving areas on both sides of the orifice 75 and comes in contact with the sensor section 3, whereby a filling completion signal is outputted to the controller 90.
However, the clutch hydraulic control apparatus disclosed in the above-described Japanese Patent Laid-open No. 63-235732 has the following disadvantage.
Since the spool 81 of the pressure control valve 80 is directly operated by the thrust force of the plunger 83 of the proportional solenoid 82, the magnitude of the thrust force of the proportional solenoid 82 has a large influence on the performance and function of the clutch hydraulic control apparatus. Namely, with use of the small-sized proportional solenoid 82, the thrust force thereof is small, thus causing a fear that malfunction of the pressure control valve 80 easily occurs when dust is caught therein. On the other hand, use of a large-sized proportional solenoid 82 to obtain a large thrust force causes an increase in the size of the clutch hydraulic control device and the cost.
The present invention is made in view of the above-described disadvantage, and its object is to provide a fluid pressure control valve apparatus for a clutch or a brake, which is small in size and capable of reducing occurrence of malfunction of the pressure control valve which is caused by dust caught therein.
In order to attain the above-described object, a fluid pressure control valve apparatus for a clutch or a brake, which controls pressure of a fluid and feeds the fluid to a clutch or a brake, according to the present invention, has a constitution including
a pressure control valve for controlling a fluid pressure to the clutch or the brake,
an electromagnetic proportional pilot operated valve for issuing an operation command for the pressure control valve with a pilot pressure corresponding to a command current applied to a proportional solenoid, and
a flow detecting valve for detecting a flow of the fluid fed to the clutch or the brake from the pressure control valve to detect completion of filling in the clutch or the brake.
According to the above constitution, the spool of the pressure control valve is operated with the pilot pressure, and therefore the spool of the pressure control valve is controlled with a large oil pressure even if the proportional solenoid is small-sized and its thrust force is small, thus making it possible to reduce malfunction of the spool caused by dust caught therein. In addition, the proportional solenoid can be made small in size, and thereby the small-sized fluid pressure control valve apparatus at low cost can be constructed. Further, the flow of the fluid to the clutch or the brake is detected with the flow detecting valve, and the completion of filling is detected according to this flow, thus making it possible to detect the completion of filling accurately without having an influence of the variation of the fed pressure of the pressure control valve caused by the line resistance and the like up to the clutch or the brake. Consequently, reliability of the fluid pressure control valve apparatus can be improved.
The fluid pressure control valve apparatus for the clutch or the brake may have the constitution in which the pressure control valve has a feedback chamber at one end side of a spool, and a pilot chamber for receiving the pilot pressure at the other end side, introduces the fluid, which is to be fed to the clutch or the brake, into the feedback chamber, balances the pressure of the fluid, which is introduced into the feedback chamber, with a magnitude of the pilot pressure generated in the pilot chamber to increase pressure of the fed fluid, and controls the pressure in a cylinder of the clutch or the brake; and
the electromagnetic proportional pilot operated valve has a valve element which moves between a fully opened state and a shutoff state of a drain outlet path of a pilot fluid introduced into the pilot chamber to control a drain outlet flow of the pilot fluid, and controls the pilot pressure by moving the valve element from the shutoff position to the fully opened position with a thrust force of a plunger of the proportional solenoid.
According to the above constitution, the electromagnetic proportional pilot operated valve for directly controlling the pilot pressure in contact with the pilot pressure receiving chamber, which is provided at the other end side of the pressure control valve, is provided, thereby making it possible to obtain the fluid pressure control valve apparatus for the clutch or the brake with a simple structure at low cost.
Further, the fluid pressure control valve apparatus for the clutch or the brake may have the constitution in which the fluid pressure control valve apparatus further includes a housing in which a first pump oil passage that communicates with a fluid pressure source, a second pump oil passage and a cylinder chamber inlet passage which communicate with a cylinder of the clutch or the brake, and a cylinder chamber fluid drain passage for draining the fluid inside the cylinder are formed,
the pressure control valve
i) is movably housed in the housing, and biased by a spring to a position to shut off the communication between the first pump oil passage and the second pump oil passage and communicate the second pump oil passage and the cylinder chamber fluid drain passage, and
ii) moves between a position to shut off the second pump oil passage and the cylinder chamber fluid drain passage from each other and communicate the first pump oil passage and the second pump oil passage, and a position to shut off the first pump oil passage and the second pump oil passage from each other and communicate the second pump oil passage and the cylinder chamber fluid drain passage, by a pressure of a clutch pressure feedback chamber that is formed at one end side to communicate with the second pump oil passage, and a pressure of a pilot pressure receiving chamber formed at the other end side,
the flow detecting valve is placed in the housing, allows a flow of the fluid, which is from the second pump oil passage to the cylinder chamber inlet passage, to flow therein via a throttle passage, and when the flow of the fluid flow via the throttle passage is stopped as a result of the fluid being filled, in the cylinder chamber inlet passage, moves by a pressure difference before and after the throttle passage to be in contact with a sensor section, and detects the filling of the fluid in the cylinder,
and the fluid pressure control valve apparatus further includes a pilot fluid inlet path which is formed inside the housing extends from the first pump oil passage via the throttle flow passage to be branched, and allows the pilot fluid to flow into the pilot pressure receiving chamber,
a pilot fluid outlet path which is formed inside the housing and drains the pilot fluid from the pilot pressure receiving chamber, and
a valve element which is placed inside the housing, and moves between a shutoff communication position, a throttled communication position by an optional amount, and a fully opened communication position, so as to connect the pilot fluid inlet path and the pilot fluid outlet path to be controllable,
the electromagnetic proportional pilot operated valve is placed at an outer wall of the housing, and
the proportional solenoid controls a pressure level of the pilot fluid in the pilot pressure receiving chamber by controlling a moving position of the valve element in order to control a moving position of the pressure control valve so that a pressure inside the clutch pressure feedback chamber and a pressure inside the pilot pressure receiving chamber balance with each other.
According to the above constitution, the inlet path for the pilot fluid, which allows the pilot fluid to flow into the pilot pressure receiving chamber of the pressure control valve via the throttle, is provided in the first pump oil passage, and therefore the first pump oil passage always has a constant flow kept by the throttle and the flow of the pump fluid which is allowed to flow into the second pump oil passage via the pressure control valve can be kept constant. Further, since the pressure control valve provides opening to communicate the first pump oil passage and the second pump oil passage in the state in which the pressure control is performed by an operation control of the electromagnetic proportional pilot operated valve, the flow of the fluid inside the first pump oil passage is kept, without a change in the inflow flow to the pilot fluid inlet path, and thus the operation control of the pressure control valve can be performed with stability.